1. Technical Field
The present disclosure relates to a method of manufacturing a microstructure to be used for delivery of an active ingredient(s) to humans or animals.
2. Related Art
Many techniques for delivering one or more active ingredients such as a pharmaceutical, nutritional, or cosmetic compound or composition thereof to humans or animals were proposed. Most common routes of delivery include non-invasive peroral (through the mouth), topical (skin), transmucosal (nasal, buccal/sublingual, vaginal, ocular and rectal), and inhalation routes. Some active ingredients, however, cannot be delivered using these routes because they are susceptible to enzymatic degradation or cannot be absorbed into humans or animals due to some reasons such as molecular size and charge issues. For thses and other reasons, some active ingredients are or have to be delivered by injection.
A conventional needle has been used for injection delivery. This transdermal needle delivery techniques, however, have some problems. For example, the techniques may cause the humans or animals subjected to the injection to feel pain and a skin thereof to be damaged, and/or may cause bleeding and/or infection in the injected area.
To solve these problems, injection techniques by using microneedles have been proposed. Advantages of the transdermal microneedle delivery techniques are, for example, that they are noninvasive, safe, hygienic, and user friendly. The microneedles are required to have some properties such as, e.g., sufficient fineness, sufficient length, and sufficient hardness for efficient delivery. More specifically, in case of a human subject, to deliver active ingredients without causing pain to a specific layer of a skin of the subject, which is composed of stratum corneum (<20 ρm), epidermis (<100 μm), and dermis (300 to 2,500 μm), the microneedles need to have a top diameter of approximately 30 μm, an effective length of 200 to 2,000 μm, and a sufficient hardness. In addition, to deliver active ingredients by biodegradable microneedles, any process that can degrade the activities of the active ingredients must be avoided, examples of which process may include a high heat treatment, an organic solvent treatment, and the like.
Methods for manufacturing a microstructure (e.g., a microstructure in which microneedles are provided) were proposed, as disclosed in, e.g., Biodegradable Polymer Microneedles: Fabrication, Mechanics and Transdermal Drug Delivery, Journal of Controlled Release 104, 2005, 5166; Polymer Microneedles for Controlled-Release Drug Delivery, Pharmaceutical Research 23, 2006, 1008; Japanese Patent Application Publication No. 2005154321; Sugar Micro Needles as Transdermic Drug Delivery System, Biomedical Microdevices 7, 2005, 185; Minimally Invasive Protein Delivery with Rapidly Dissolving Polymer Microneedles, Advanced Materials 2008, 1; Dissolving Microneedles for Transdermal Drug Delivery, Biomaterials 2007, 1; and U.S. Patent Application Publication No. 20080157421 A1.
Some of the methods, however, do not provide a microstructure having microneedles that have sufficient (top) diameter, sufficient length, and sufficient hardness and some of the methods involve degradation of the activity of active ingredients. Thus, there is still a need for a method for manufacturing a microstructure having desired properties in a simpler and more cost-effective way.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.